Chart drive system

ABSTRACT

A chart drive system adapted for use with a multi-channel recorder. A spring retainer array is provided for holding and dispensing a chart from a chart supply roll. The chart is trained from the supply roll over a two-speed drive roll provided with multiple spaced-apart drive belts, including a center control belt having teeth thereon adapted to engage perforations in the chart. A writing platen is positioned beneath the chart downstream of the drive roll and pivotably attached to the drive roll. A take-up roll is positioned inwardly of the writing platen, adapted to be driven by a motor through a slip clutch so that the take-up roll tension balances back tension on the chart with respect to the supply roll. Paper guides are provided beneath the chart at the ends of the drive roll.

Kampf United States Patent [1 1 4 1 Feb. 19, 1974 CHART DRIVE SYSTEM[75] Inventor: Richard S. Kampf, Costa Mesa,

Calif.

[73] Assignee: Beckman Instruments, Inc.,

Fullerton, Calif.

[22] Filed: Jan. 17, 1972 [21] Appl. No.: 218,397

[52] US. Cl. 242/67.3 R, 346/136 [51] Int. Cl. B65h 17/02, 601d 15/29[58] Field of Search 242/673, 67.2; 346/136 [56] References Cited UNITEDSTATES PATENTS 1,551,415 8/1925 Marcellus 242/673 R 2,556,812 6/1951Jordan 346/136 2,524,564 10/1950 Gorham 226/196 2,845,232 7/1958 Johnson242/672 2,693,917 11/1954 Kindler 242/67.2

3,154,368 10/1964 I Daigler 346/145 X 3,113,823 12/1963 Phillips 346/1362,796,317 6/1957 Valenti 346/136 3,281,090 10/1966 Baronowski 242/67.3 R

Primary ExaminerGeorge F. Mautz Assistant ExaminerEdward J. McCarthyAttorney, Agent, or FirmPaul R. Harder; James M. Thomson; Robert J.Steinmeyer [57] ABSTRACT A chart drive system adapted for use with amultichannel recorder. A spring retainer array is provided for holdingand dispensing a chart from a chart supply roll. The chart is trainedfrom the supply roll over a two-speed drive roll provided with multiplespacedapart drive belts, including a center control belt having teeththereon adapted to engage perforations in the chart. A writing platen ispositioned beneath the chart downstream of the drive roll and pivotablyattached to the drive roll. A take-up roll is positioned inwardly of thewriting platen, adapted to be driven by a motor through a slip clutch sothat the take-up roll tension balances back tension on the chart withrespect to the supply roll. Paper guides are provided beneath the chartat the ends of the drive roll.

4 Claims, 4 Drawing Figures PATENTEDFEB 1. 3.792.825

sum 2 0F 2 CHART DRIVE SYSTEM BACKGROUND OF THE INVENTION The presentinvention relates to a chart drive system that is especially adapted foruse with a multi-channel chart recorder. More particularly the inventionconcerns such a chart drive system wherein the chart is moved underuniform tension without excessive wander with respect to the recordingmeans, so that recording errors due to the chart transport system arereduced.

Direct writing strip chart recorders are widely used in industry inconjunction with process control systems and other instruments where itis desired to make a continuous log of the measured output of aparameter. Such recorders utilize either pressure sensitive orelectro-sensitive paper, or pen and ink systems operated by servocontrol systems responsive to the measured parameters of the system. Inall cases, the recorders generally utilize a chart drive system formoving the chart with respect to writing instruments positioned in oneor more channels of the recorder. Thus the strip chart drive systemserves to dispense, continuously, the chart from a supply roll, to trainthe chart past a writing station, and then to restore the chart, such asupon a takeup roll.

Errors in direct writing recorders can result from inaccuracies in thepen servo system, in the chart paper and printing thereon, in the charttransport system, and in the calibration of the overall system,Therefore, in order to achieve satisfactory results, it is desirable tominimize the errors occurring in the chart transport system, as well asany errors the chart transport contributes to other parts of the overallsystem.

Errors directly occurring in chart transport systems sometimes resultfrom wander of the chart paper back and forth with respect to the driveroll. Such errors can be due to end shake in the drive roll or loosefitting sprocket holes and sprocket teeth. Error can also occur in thechart drive system due to uneven back tension on the paper, as well asnonuniform drive tension across the width of the chart. Such errorsoccur particularly with pressure sensitive paper systems since theyrequire high stylus pressure and correspondingly'higher paper tension.In addition to such errors, any error which occurs in the chart due tovariations in the position of grid lines printed on the chart, orhumidity caused changes in size of the chart paper, can be minimized bythe use of a properly designed chart drive system.

SUMMARY for THE INVENTION.

Accordingly, it is a general purpose of this invention to provide asimple, low cost chart drive system which can be easily used by anoperator. In addition it is envisioned that the chart drive systemdescribed will be able to store anadequate supply of chart paper on asupply roll and continuously dispense the chart paper therefrom whilethe system maintains adequate and uniform back tension on the chartpaper. In addition it is envisioned that the chart drive system willdrive the chart paper at one of two predetermined speeds past arecording station, and will enable the operator to view the recordingsupon the chart after it leaves the recording station. Furthermore, thechart drive system will include a back-up surface or platen for thechart over at least a portion of its movement so that an operator canview the chart or write upon the chart, and the system will otherwiseinclude means for restoring the chart paper.

These purposes are attained in a chart drive system that is especiallyadapted for use with a multi-channel chart recorder. The chart used inthe system is to be stored upon a supply roll which is held in a springre tainer, adapted to handle rolls of different sizes and to dispensechart paper therefrom. The chart is trained along a continuous reachfrom the supply roll over a two-speed drive roll provided with multiple,spacedapart drive belts having teeth adapted to engage perforationsformed in the chart. A control belt is centered with respect to thechart to minimize the errors arising from the chart expansion. The driveroll is adapted to move the chart paper past a recording station andover a platen, which is positioned under a portion of the chart so thatthe operator can view and write upon the chart after it passes therecording station. The platen is pivotably attached to the ends of thedrive roll whereby it can be pivoted upwardly to provide access totake-up roll positioned inwardly of the writing platen. The takeup rollis motor driven, through a slip clutch, so that the chart can beselectively unrolled off of the take-up roll and rewound withoutdisturbing the positioning of the portion of the chart located in therecording station. Paper guides are provided at each end of the driveroll, positioned beneath the paper, to cause the paper to conform to thecurvature of the drive belts to eliminate any looseness of the chartpaper over the ends of the drive roll.

BRIEF DESCRIPTION OF THE DRAWINGS These and other features and objectsof the invention will become apparent from the following detaileddescription of the invention, when considered with the accompanyingdrawings wherein:

FIG. 1 is a perspective view of one embodiment of the invention with thechart paper partially broken away;

FIG. 2 is an end view, in section, of the embodiment illustrated in FIG.1;

FIG. 3 is a front view of the embodiment illustrated in FIG. '1 with thewriting platen omitted; and

FIG. 4 is a partial end view of the embodiment illustrated in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings andparticularly to FIG. 1, a chart drive system 10 is generally illustratedcomprising a frame 12 including spaced apart end plates 14, 16 rigidlyjoined together by cross members 18,20. The end plates can be fabricatedof any suitable material, such as light metal or plastic and are ofsuitable dimension to provide the necessary strength to support theother components of the system. The outline of the end plates isgenerally countoured in the embodiment illustrated, to provide mountinglocations for all of the components of the system beneath the peripheraloutline of the end plates, although this is not essential. Cross members18, 20 are likewise fabricated of metal or plastic and are secured tothe end plates by any suitable means, such as by rivets 21 extendingthrough collars 22 formed in the end plates, adapted to receive the endsof the cross members.

A supply roll station 30 is defined between the end plates at the rearof the chart drive system, including a pair of pads 32, 33 secured,respectively, to end plates 14, 16. Pads 32, 33 are each oriented at anangle with respect to the chart roll as best seen in FIG. 2, for apurpose described hereinafter. The pads are preferably formed of metalor other suitable material, and each has a coating 34 of a softresilient material, such as foam rubber.

The supply roll station otherwise includes a pair of inverted, U-shapedspring members 36, 37 secured to cross member 18. The spring members arespaced apart and located substantially opposite to pads 32, 33,respectively. Each spring member has one relatively straight, fixed sideand a movable side having a curved section 39 formed therein, adapted togenerally match the curvature of a cylindrical chart roll such as roll93 adapted to dispense chart paper. In addition, the lower ends of thespring members have slots 41 formed therein, adapted to engagewireguides 42 extending between cross members 18, 20. Accordingly,movement of the free end of the spring member is possible to retainforce on the supply roll and clamp it in the chart drive as the supplyroll diameter decreases. To provide additional force, tension springs46, 47 are connected between the lower end of members 36, 37 and crossmember 20. The surfaces of spring members 36, 37 that are adapted toface the supply roll are coated with a coating 44 of Teflon or someother material having a low coefficient of friction.

A drive roll 51 is illustrated supported between end plates 14, 16. Thedrive roll includes an inner shaft 52 rotatably supported in bearings54, 55 that are secured in suitable openings in the end plates. Inaddition the drive roll includes a cylindrical outer portion 57 securedto shaft 52 extending the full width of the chart. Portion 57 is formedwith three spaced-apart sets of gear teeth 58 formed or idented therein.One set of gear teeth is located at the center of portion 57 of thedrive roll and each of the other sets of gear teeth is spaced inwardlyfrom one of the opposite ends of portion 57.

An idler shaft 61 is provided, supported between end plates 14, and 16secured to the end plates. The idler shaft is positioned at a locationjust beneath and vertically aligned with the drive roll shaft. Threeidler pulleys 68 are rotatably secured on shaft 61, spaced at locationscorresponding to the locations of drive gear teeth 58. Each of thepulleys is of identical diameter, and the diameter is selected to beslightly larger than the diameter of outer portion 57 of the drive roll.A

7 drive belt 70 is provided for each drive gear 58 and pulley 68. Eachdrive belt is a continuous flexible belt having teeth 71 formed on aninner surface thereof adapted to match and engage the correspondingteeth of gear 58. In addition each drive belt has teeth 72 protruding inan aligned pattern from the outer surface thereof, adapted to engagecorresponding perforations in the chart paper so that the drive belt,when rotated, serves to move the chart paper through the chart drivesystem. Since the outline of the belts 70 and pulleys 68 extend slightlybeyond the edge of the chart roll as shown in FIG. 2, the belts firmlyengage and drive the chart paper even when the supply roll is nearlydepleted.

Gears 58 and drive belts 70 are of substantially corresponding width sothat the drive belts do not wander with respect to the ends of the driveroll. Furthermore, the teeth of the center drive belt designated as thecontrol belt are sized toengage the perforations in the chart .withoutexcessive tolerance. Accordingly the chart paper is not able to wanderback and forth on the drive roll during movement thereof. However, thechart paper is provided with elongate slots at the end location's,corresponding to the end drive belts. Consequently, as the width of thechart expands or contracts, due to humidity of temperature changes, thechart still fits the reach between the end drive belts. Furthermore,since the center drive belt is used as the control belt, any sidemovement of the chart with respect to the drive belts and stylii of therecorder is divided into two equal components. This has the effect ofreducing the chart error due to such expansion by a factor of two. Asynchronous motor 75 is mounted upon a platform 74 secured to end plate14, and a conventional overruning clutch 76 is provided for transferringmotive power from motor 75 to shaft 52 through a conventional gearingsystem 77. In addition a synchronous motor is provided along with aconventional overunning clutch 86 also adapted to provide motive powerto shaft 52. Synchronous motors 75, 85 are adapted to operate atdifferent speeds, and the overrunning clutches enable the selection ofone or the other of the motor speeds in accordance with the desiredchart speed of the system for a given purpose. The use of overrunningclutches enables energization of one of the motors without interferencefrom the non-energized motor.

A cylindrical take-up roll 91 is provided extending between the endplates at a location just beneath the idler shaft. The take-up roll hasa suitable diameter to permit the roll to be inserted through the hollowcenter of a conventional chart supply roll, such as roll 93. The take-uproll is removably suspended with respect toend plate l4, 16. Thus, oneend of take-up roll 91 is adapted to releasably engage a rotatable pinextending through end plate 14. The other end of the take-up rollincludes a spring loaded extension 92 adapted to fit into acorresponding notch 94 formed in the edge of end plate 16. A pin 97 isprovided, extending transversely through the center of roll 91. Pin 97is adapted to engage a corresponding slot formed in the end of the chartsupply roll when roll 91 is inserted therethrough. Accordingly, rotationof roll 91 serves to rotate the chart supply roll and rewind a chartthereon.

A torque motor is also supported on platform 74, operatively connectedto pin 90 and roll 91 by a slip clutch 106. Motor 105 provides positivetorque for rotating roll 91, with the slip clutch permitting handrotation of roll 91 in an opposite direction to facilitate unrolling ofthe chart for various purposes, as is explained hereinafter.

An elongate platen 121 is provided, extending be tween end plates 14, 16on the front side of the chart drive system with the chart paper trainedthereover. The platen comprises a wide plate 122 having an outwardlyextending or slightly convex curvature adapted to support the chartpaper and facilitate the movement of the chart paper thereover. Theplaten can serve as a base for supporting the chart during a recordingoperation. In addition, the platen permits the operator to view thechart, after recording, and to make hand markings thereon, if that isdesired.

To facilitate use of the platen, it is pivotally mounted by end brackets124, 125, each having one end secured at a respective upper corner ofplate 122. The other end of each bracket is pivotally secured to acorresponding end of shaft 52 of the drive roll. Accordingly,

the platen can assume a lowered position as illustrated in FIG. 2, witha stop 126 extending from the lower corner of plate 122 being located inengagement with a corresponding edge of end plate 14. In this positionthe chart can be selectively advanced over the platen and recordingoperations can be carried out. The platen can also be pivoted or raisedto an elevated position, such as that illustrated in dashed outline inFIG. 2. With the platen raised, easy access is afforded to the take-uproll to provide replacement or respooling of the latter. The platen canbe easily elevated with the chart paper present, in view of the use ofthe slip clutch between the take-up roll and its driving motor.

The chart drive system otherwise includes paper guides 111, 112 securedon end plates 14, 16 respectively, at a location just beneath drive roll51. The paper guides comprise elongate, relatively wide bands ofmaterial having rounded edges 117 to prevent hangup of the chart paperthereon. The guides are secured to the end plates so that the paperguides engage the chart paper trained over the main drive roll. Thiscauses the paper to conform to the curvature of the drive belts andprevents looseness of the chart paper at the ends of the roll wherebyrecording inaccuracy due to such looseness is eliminated.

In the use of the chart drive system described herein, a supply roll ofchart paper is inserted into the supply roll station with the chartpaper adapted to unroll from the right side of the roll as viewed inFIG. 2, and the roll rotating in a counterclockwise direction. Thespring members tightly engage supply rolls of various sizes, and due tothe spring force, maintain a firm grip on the roll as its size decreasesdue to usage. The provision of a high friction foam rubber coating onpads 32, 33 and a low friction Teflon coating on spring members 36, 37results in substantially uniform back tension on the roll as the chartpaper is dispensed.

In view of the locationof pads 32, 33, slightly inwardly of the outerperiphery of pulleys 68, good contact is ensured between the drive beltsand the chart as the initial point of contact therebetween. In addition,due to the reduced diameter of drive roll 51 with respect to pulleys 68,good contact is maintained as the chart is drawn over the top of thedrive roll. The paper guides serve to remove looseness in the chart atthe .ends of the roll and eliminate any errors caused thereby. Since thedrive belts afford good traction with respect to the chart both beforeand after the chart passes the top of the drive roller and the recordingstation no additional means are necessary to advance the chart after itleaves the recording station. Consequently the chart drive can beoperated without a take-up roll, if desired, with the chart paperpermitted to drop down under its own weight.

In the embodiment described the chart is trained over the writing platenand wound upon the take-up roll. The torque provided by motor 105 is notsufficient to overcome the torque provided to the main drive roll. Theuse of slip clutch 106 permits the writing platen to be withdrawnupwardly so that the take-up roll is easily accessible. In addition itpermits an operator to withdraw substantial portions of the chart fromthe take-up roll for re-examination. After such re-examination, theoperator can utilize motor 105 to rewind the loose portion of the chartwithout interferring with the recording operation.

It should be apparent that the chart drive system described herein isextremely simple in design and inexpensive to construct and use. Inaddition the drive system enables the storage and use of large chartsupply rolls, and the continuous dispensing of charts therefrom with thechart under balanced tension. Further more the system provides movementof the chart at one of two predetermined speeds and provides a view ofthe chart after it leaves the drive roll. Finally the system provides aback-up surface so that the operator may write on the chart in theviewing area, before the paper is respooled on a take-up roll driventhrough the slip clutch.

All of these features are provided in a chart drive system which isintended to minimize side to side wander of the chart and expansionerror with respect to the recording stylii, and eliminate excessivelooseness in the chart at the ends of the drive roll. Accordingly, thechart drive system described is especially useful in systems whichrequire multi-channel recording.

I claim:

1. A chart drive assembly including a frame comprising two end platessecured in spaced opposed relationship by at least one cross member;

a supply roll station on said frame including a pair of pads secured tosaid frame, a different one of said pads being located adjacentdifferent ones of said end plates and a pair of spring members securedto said frame, a different one of said spring members being spaced fromand generally opposed to different ones of said pads, said springmembers having a curved section formed therein adapted to generallymatch the curvature of a cylindrical supply roll and hold said supplyroll between said spring members and said pads;

a platen secured upon said frame;

chart drive means rotatably secured upon said frame between said endplates for selectively advancing paper from a supply roll past arecording station and over said platen;

a take-up roll rotatably secured between said end plates proximate saidplaten for restoring paper from said chart after it passes saidrecording station; and

take-up roll drive means secured to said take-up roll through a slipclutch.

2. The chart drive assembly of claim 1 wherein said pads are providedwith a coating of resilient material having a relatively highcoefficient of friction and wherein said spring members are providedwith a coating of material having a relatively low coefficient offriction whereby drag is exerted upon the paper as it is dispensed fromsaid roll adjacent said pads.

3. A chart drive assembly including a frame;

supply roll station means secured upon said frame for resilientlygripping a roll of chart paper and providing a predetermined drag onsaid roll;

a platen secured upon said frame;

chart drive means secured upon said frame for providing forward tensionon said roll to selectively advance paper from said roll past arecording station and over said platen, said drive means including adrive roll rotatably secured upon said frame, said drive roll havingthree spaced apart sets of gear teeth formed therein, one set of gearteeth being located at the central portion of said drive roll anddifferent ones of the other sets of gearteeth being spaced inwardly fromrespective ones of the oppo site ends of said drive roll;

a plurality of idler pulleys rotatably supported upon said frame, anidler pulley being spaced from and aligned with each of said sets ofgear teeth formed in said drive roll;

a plurality of drive belts, each drive belt being continuously flexibleand having teeth formed on the inner surface thereof for engagingrespective ones of said idler pulleys and sets of gear teeth formed insaid drive roll, each drive belt having chart drive teeth protrudingfrom the outer surface thereof and adapted to engage perforations in thechart paper for driving said paper; power means secured to said driveroll through an overrunning clutch for operating said chart drive means;and a a take-up roll rotatably secured upon said frame for taking uppaper from said supply roll station after it passes a recording station.

4. The chart drive assembly of claim 3 wherein the projections extendingfrom the outer surface of the centrally located drive belt are adaptedto engage, without play in any direction, perforations formed in saidpaper and said projections extending from the outer surface of the otherof said drive belts being adapted to engage perforations formed in saidchart paper without play in the direction of drive but allowing lateralmovement of the chart paper with respect thereto.

1. A chart drive assembly including a frame comprising two end platessecured in spaced opposed relationship by at least one cross member; asupply Roll station on said frame including a pair of pads secured tosaid frame, a different one of said pads being located adjacentdifferent ones of said end plates and a pair of spring members securedto said frame, a different one of said spring members being spaced fromand generally opposed to different ones of said pads, said springmembers having a curved section formed therein adapted to generallymatch the curvature of a cylindrical supply roll and hold said supplyroll between said spring members and said pads; a platen secured uponsaid frame; chart drive means rotatably secured upon said frame betweensaid end plates for selectively advancing paper from a supply roll pasta recording station and over said platen; a take-up roll rotatablysecured between said end plates proximate said platen for restoringpaper from said chart after it passes said recording station; andtake-up roll drive means secured to said take-up roll through a slipclutch.
 2. The chart drive assembly of claim 1 wherein said pads areprovided with a coating of resilient material having a relatively highcoefficient of friction and wherein said spring members are providedwith a coating of material having a relatively low coefficient offriction whereby drag is exerted upon the paper as it is dispensed fromsaid roll adjacent said pads.
 3. A chart drive assembly including aframe; supply roll station means secured upon said frame for resilientlygripping a roll of chart paper and providing a predetermined drag onsaid roll; a platen secured upon said frame; chart drive means securedupon said frame for providing forward tension on said roll toselectively advance paper from said roll past a recording station andover said platen, said drive means including a drive roll rotatablysecured upon said frame, said drive roll having three spaced apart setsof gear teeth formed therein, one set of gear teeth being located at thecentral portion of said drive roll and different ones of the other setsof gear teeth being spaced inwardly from respective ones of the oppositeends of said drive roll; a plurality of idler pulleys rotatablysupported upon said frame, an idler pulley being spaced from and alignedwith each of said sets of gear teeth formed in said drive roll; aplurality of drive belts, each drive belt being continuously flexibleand having teeth formed on the inner surface thereof for engagingrespective ones of said idler pulleys and sets of gear teeth formed insaid drive roll, each drive belt having chart drive teeth protrudingfrom the outer surface thereof and adapted to engage perforations in thechart paper for driving said paper; power means secured to said driveroll through an overrunning clutch for operating said chart drive means;and a take-up roll rotatably secured upon said frame for taking up paperfrom said supply roll station after it passes a recording station. 4.The chart drive assembly of claim 3 wherein the projections extendingfrom the outer surface of the centrally located drive belt are adaptedto engage, without play in any direction, perforations formed in saidpaper and said projections extending from the outer surface of the otherof said drive belts being adapted to engage perforations formed in saidchart paper without play in the direction of drive but allowing lateralmovement of the chart paper with respect thereto.